My daughter was born in Barrow much to her dismay! As for seeing the subs, I doubt very much you'll catch a glimpse, now and again sections are moved across town from one dockyard building to another. Once in a blue moon they also sail completed ones out through Walney channel, but again you'd be lucky to see that happening.
Whilst there's very little to commend Barrow itself as a destination, nearby is Walney Island which is a pleasant place to visit. I used to Sea Kayak out from Roa Island towards Peil Island for a pint in the the pub, then on to the Southern tip of Walney to watch the seals. The landlord of the Piel Island pub is also designated the King of Piel island. I also spent many a happy hour wandering the nature reserves there, whilst I lived in nearby Ulverston. Ulverston is also a very pleasant little town, or at least it was, I've not been back since I lived there in the early noughties.